1. Field
Example embodiments relate to a robot actuator, in which efficiency in force reflection and back-drivability is improved, and a humanoid robot having the same.
2. Description of the Related Art
In general, robots have increasingly been used in all industries, and particularly, research and development of humanoid robots have been accelerated. In order to allow a humanoid robot to conduct operations including household affairs on behalf of humans, achievement of various motions is important.
In order to achieve these various motions, the humanoid robot includes a joint driving apparatus to drive a joint in various directions.
The joint driving apparatus includes a plurality of actuators. Each of the actuators includes a motor, a driving force transmission unit to convert driving force of the motor into a rectilinear motion to be transmitted to a slider. The slider may move in the lengthwise direction of the actuator through the driving force transmission unit.
The driving force transmission unit includes a ball screw and a linear guide disposed parallel with the ball screw to guide the rectilinear motion of the slider. The ball screw and the linear guide are connected by the medium of the slider.
A wire is connected to the slider, and thus moves according to the rectilinear motion of the slider. A joint is rotated by moving the wire, and thus a link connected to the joint is operated.
However, torsion is applied to the driving force transmission unit in the direction of force, inversely applied to the driving force transmission unit. Since the ball screw is separated from a screw axis by a designated distance, when the ball screw receives force from a long distance, torsion as well as force for the rectilinear motion is applied to the ball screw. Due to the above torsion, efficiency in force reflection and back-drivability of the actuator are lowered.
Further, in order to withstand torsion, sizes of the ball screw and the linear guide in the driving force transmission unit are increased, and design of the actuator is hampered by many restrictions.
Moreover, machining accuracy of the ball screw and the linear guide of the driving force transmission unit needs to be increased to accurately assemble the two parts, and conventionally, assembly performance of the two parts is lowered.